This has happened to me before when the 'host name' field is blank - do you have the host name field populated with the value of the target system?
I rebooted the receiver and it started polling most of the hosts. I still have some that listed as inactive. The reciever isn't polling hosts that use DHCP. I checked the log anf this is what I'm getting for DHCP hosts (these are windows 10 machinnes)
w/ NTStatus: NT_STATUS_INVALID_INFO_CLASS - Invalid information class